So far, the technology used for producing bi-metallic (or bi-colored) coins, hereafter named bi-metallic ring technology, has consisted on the utilization of an inner disk (center) and an outside ring of different materials, generally with different colors.
The coins are produced in two stages: firstly the center is placed inside the outer ring with a little clearance, and secondly the two parts are assembled together with the impartion of the surface details by the minting dies (FIG. 1). In the last years, several technical solutions for ensuring the mechanical joint between the inner disk and outside ring, have been developed by the producers of disk blanks, manufacturers of presses as well as by the mint houses.
More recently, a new type of bi-metallic collection coin has been presented, in which the bi-colored effect is achieved by mounting a small foil over a limited zone of the surface of a disk blank.
FIG. 1 is an exploded sectional view of a two part prior art medal or coin.
FIG. 2 is an exploded sectional view of two different blanks used in the formation of medals or coins of the present invention.
FIG. 3 is an exploded view, partially in section, of a die set performing the preforming step of the present invention on a medal or coin.
FIG. 4 is an exploded view, partially in section, of a rimming die set performing the rimming step of the present invention on a medal or coin.
FIG. 5 is a sectional view of two medals or coins, one before and the other after the joining step of the present invention.
FIG. 6 is an exploded view, partially in section, of a die set performing the imprinting step of the present invention.